Original ideas about Abraham Lincoln are uncommon. Given the ever-growing pile of Lincoln books and articles, not much remains unsaid or probably even unthought about the man. So on the rare occasion that somebody does think an original thought about him, the thinker (or in this case thinkers) deserve praise merely for the deed.

David Hirsch and Dan Van Haften’s originality comes from their having taken a fact well-known to Lincoln scholars—that he read and mastered Euclid’s Elements of Geography—and made that fact the centerpiece of his intellectual universe. “His self-development was actually more of an engineering accomplishment than an exercise of innate talent,” they argue, with Euclid being “the bone upon which Lincoln laid his muscle of reason. Lincoln transformed geometry into speech” (xvii). They meticulously deconstruct a number of Lincoln’s speeches and letters—everything from his famous “House Divided” Speech to jury arguments he made as an attorney—and show that Euclidian principles structured his oratory and writing, providing much of Lincoln’s powerful logical force.

The authors carry this approach still further by arguing that Lincoln’s studies in math and geometry were augmented by his legal education and the rigorous training in logical thinking and debate he received during his nearly quarter-century’s worth of experience at the Illinois bar. His legal career “developed his analytical and communication skills,” Hirsch and Van Haften argue, “He practiced marshaling relevant facts and law; he organized thoughts and stated arguments clearly and logically. With these tools Lincoln did battle on legal and political fronts” (15).

The twin pillars of Euclid and the law provided “the structure of reason,” the subtle but indispensable framework for Lincoln’s remarkable intellectual growth, and later his success as president. Hirsch and Van Haften see greatness in Lincoln’s ability to apply a few basic mathematic and legal reasoning principles to the problems of his age, and to make his case—for limiting slavery’s growth, for preserving the Union, for emancipation and winning the war—with the irrefutable logic of those principles.

Hirsch and Van Haften are an attorney and a mathematical engineer, respectively. They know their business, and there is much to like and to learn from their expertise. No previous scholars have so systematically and minutely examined and laid bare the considerable influence of geometry and the law on Lincoln’s thinking. They make a convincing case. Reading their side-by-side, sometimes almost sentence-by-sentence juxtaposition of, for example, Lincoln’s 1860 Cooper’s Union Address with Euclid’s “elements of a proposition,” and the influence of the latter upon the former is unmistakable.

Kudos, then, to Hirsch and Van Haften for their creativity, their insight and their ability to reveal heretofore hidden substrata in Lincoln’s writing, speaking and thinking. They have made a valuable contribution to Lincoln scholarship.

Neverthelesss, Abraham Lincoln and the Structure of Reason is a flawed book, oddly lacking in the very qualities of clarity and focus the authors find so praiseworthy in Lincoln. Hirsch and Van Haften possess a barely restrained, almost giddy enthusiasm for what they seem to think is the answer to Lincoln’s mind. “This is a story about a man with a secret ready to be revealed,” they write, and that “secret”—Euclidean and legal logic—“has been hiding in plain sight” overlooked by generations of Lincoln scholars until only now here revealed for the first time (xvii, 1). “Historians looked at Lincoln’s oratory and his writing to explain his greatness,” Hirsch and Van Haften argue, “But these admirers remain unaware of the underlying structural mechanism….Many who looked for the sixteenth president’s secret skirted the edges but did not persevere to the prize” (xviii, xxii).

There is a fair amount of off-putting hubris in such a statement, not to mention mono-causality. Having demonstrated with admirable clarity the influence of Euclid and the law, was it necessary to pitch this influence as some sort of rosebud in Lincoln’s psyche that explains everything and has eluded everyone—until this book came along? At times, the authors’ tendency towards exaggeration is jaw-dropping. “About 2,300 years previously Euclid had compiled a definitive summary of geometry. By looking back at it, Abraham Lincoln not only won cases for his clients but ultimately saved his nation” (23).

Showing that Euclid and the law mattered to Lincoln was worthwhile and useful; trying to show that they were the root cause not only of his greatness but Union victory was over-reach, and entirely unnecessary. But then, Abraham Lincoln and the Structure of Reason is packed with much that is unnecessary. The authors burden their arguments with endless forays into tangential subjects: how to properly choose a lawyer, the nature of twentieth-century legal education, the sad neglect of classical math and geometry in modern schools, even a gratuitous swipe at Google. The result is a meandering narrative that is confusing, incomprehensibly organized, and nearly unreadable.

At bottom, Abraham Lincoln and the Structure of Reason is a useful but frustrating book. Hirsch and Van Haften’s argument is original and analytically sound. But it is presented in an uneven, overwrought manner that makes their book difficult to digest and creates unnecessary obstacles for any reader who wishes to understand Abraham Lincoln’s mind. Often praising Lincoln for his sharply focused, finely tuned Euclidian logic, it is both strange and unfortunate that Hirsch and Van Haften did not see fit to apply these qualities to their own writing.

Brian Dirck is a Professor of History at Anderson University and the author of numerous books about Abraham Lincoln including the soon-to-be-released Abraham Lincoln and White America.